New: virtual machine with assembler.

This commit is the start of compiler work to make TXR Lisp
execute faster. In six days of part time work, we now have a
register-style virtual machine with 32 instructions, handling
exceptions, unwind-protect, lexical closures, and global
environment access/mutation. We have a complete assembler and
disassembler for this machine. The assembler supports labels
with forward referencing with backpatching, and features
pseudo-ops: for instance the (mov ...) pseudo-instruction
chooses one of three kinds of specific move instruction based
on the operands.

* Makelfile (OBJS): Add vm.o.

* eval.c (lookup_sym_lisp1): Static function becomes external;
the virtual machine needs to use this to support that style
of lookup.

* genvmop.txr: New file. This is the generator for the
"vmop.h" header.

* lib.c (func_vm): New function.
(generic_funcall): Handle the FVM function type via new
vm_execute_closure function. In the variadic case, we want
to avoid the argument copying which we do for the sake of C
functions that get their fixed arguments directly, and then
just the trailing arguments. Thus the code is restructured a
bit in order to switch twice on the function type.
(init): Call vm_init.

* lib.h (functype_t): New enum member FVM.
(struct func): New member in the .f union: vm_desc.
(func_vm): Declared.

* lisplib.c (set_dlt_entries_impl): New static function,
formed from set_dlt_entries.
(set_dlt_entries): Reduced to wrapper for
set_dlt_entries_impl, passing in the user package.
(set_dlt_entries_sys): New static function: like
set_dlt_entries but targetting the sys package.
(asm_instantiate, asm_set_entries): New static functions.
(lisplib_init): Auto-load the sys:assembler class.

* share/txr/stdlib/asm.tl: New file.

* vm.c, vm.h, vmop.h: New files.

1 files changed, 3 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index f80f497a..ca72f970 100644
--- a/lib.h
+++ b/lib.h
@@ -70,6 +70,7 @@ typedef enum type {
 typedef enum functype
 {
    FINTERP,             /* Interpreted function. */
+   FVM,                 /* VM function. */
    F0, F1, F2, F3, F4,  /* Intrinsic functions with env. */
    N0, N1, N2, N3, N4, N5, N6, N7, N8   /* No-env intrinsics. */
 } functype_t;
@@ -148,6 +149,7 @@ struct func {
   val env;
   union {
     val interp_fun;
+    val vm_desc;
     val (*f0)(val);
     val (*f1)(val, val);
     val (*f2)(val, val, val);
@@ -890,6 +892,7 @@ val func_n1ov(val (*fun)(val, varg), int reqargs);
 val func_n2ov(val (*fun)(val, val, varg), int reqargs);
 val func_n3ov(val (*fun)(val, val, val, varg), int reqargs);
 val func_interp(val env, val form);
+val func_vm(val closure, val desc, int fixparam, int reqargs, int variadic);
 val func_get_form(val fun);
 val func_get_env(val fun);
 val func_set_env(val fun, val env);